1. Field of the Invention
The present invention relates to an oscillating device having a movable plate capable of oscillating about a torsion center axis and a method of producing the same. Furthermore, this invention relates to an optical deflector, an optical scanner, an electro-photographic image-forming apparatus, and a projection-type image display apparatus, such as a display, which are provided with the oscillating device.
2. Related Background Art
FIG. 14 is a perspective view of a resonant scanner described in Japanese Patent Application Laid-Open No. 2001-305471. Reference numeral 801 denotes a silicon substrate, reference numeral 802 denotes a movable part, reference numeral 803 denotes a torsion bar serving as an elastic supporting part, reference numeral 804 denotes a coil, reference numeral 805 denotes a total reflection mirror, reference numerals 806 and 807 denote permanent magnets, and reference numeral 808 denotes an electrode.
In this resonant scanner, the movable part 802 and the torsion bar 803 which supports the movable part 802 in such a manner that the movable part is capable of angular displacement with respect to the silicon substrate 801 are formed integrally with the silicon substrate 801, the coil 804 which allows application of a movable part driving current is provided on a periphery of the movable part 802, the total reflection mirror 805 is provided at the center of the movable part 802, and the permanent magnets 806 and 807 which apply a static magnetic field to opposing sections of the coil 804 on the movable part 802 which are parallel to the axial direction of the torsion bar 803 are disposed with the S pole of one and the N pole of the other facing to each other. This arrangement is also called a galvanometer mirror.
FIG. 15 is a perspective view of a scan mirror described in Japanese Patent Application Laid-Open No. 6-82711. Reference numeral 901 denotes a mirror surface part, reference numeral 902 denotes a supporting member, reference numeral 903 denotes a permanent magnet, reference numeral 904 denotes a glass plate in the shape of a rectangular plate, reference numeral 905 denotes a semiconductor substrate and reference numeral 906 denotes a coil.
In this optical deflector, the mirror surface part 901 is provided on one surface of the movable plate 904, the permanent magnet 903 is magnetized to have opposite poles at the supporting members 902 on the opposite sides thereof and is provided on the other surface of the glass plate 904, and the coil 906, which is spiral and in the shape of a foil, is provided on the semiconductor substrate 905, such as of silicon, which is disposed to be in opposition to the permanent magnet 903.
The arrangement shown in FIG. 14 results in a large size, since the permanent magnets are disposed at the sides of the total reflection mirror.
The arrangement shown in FIG. 15 allows the glass plate to be oscillated only slightly, since the coil is disposed below the plate. In order to oscillate the glass plate largely, the gap between the coil and the glass plate needs to be increased, resulting in a large size arrangement. Furthermore, to oscillate the glass plate largely while maintaining the increased gap, a larger amount of current has to be supplied to the coil.